ArmPkg/ArmArchTimerLib: Promotes 32bit value to prevent overflow

ArmPkg/ArmArchTimerLib: Promotes 32bit value to prevent overflow

Both MicroSeconds and PcdArmArchTimerFreqInHz are 32-bit values on
AArch32 so their multiplication produces 32-bit result that might
cause wrong calculation.

Example: With MicroSeconds = 200 us, PcdArmArchTimerFreqInHz = 24MHz.
200*24000000 = 0x1_1E1A_3000 => So 0x1E1A_3000 when the type is UINT32.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16329 6f19259b-4bc3-4df7-8a09-765794883524